VPIM Working Group Glenn Parsons
Internet Draft Janusz Maruszak
Document: <draft-ema-vpim-clid-05.txt> Nortel Networks
Category: Standards Track October 2002
Calling Line Identification for Voice Mail Messages
Status of this Memo
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Abstract
This document describes a method for identifying the originating
calling party in the headers of a stored voice mail message. Two
new header fields are defined for this purpose: CallerÏID and
CalledÏName. CallerÏid is used to store sufficient information for
the recipient to callback, or reply to, the sender of the message.
Called-name provides the name of the person sending the message
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Table of Contents
1. Introduction....................................................3
2. Conventions used in this document...............................3
3. Calling Line Identification Field...............................4
3.1 Internal Call...............................................4
3.2 External Call...............................................4
3.3 Numbering Plan..............................................5
4. Caller Name Field...............................................5
5. Formal Syntax...................................................6
5.1 Calling Line Identification Syntax..........................6
5.2 Caller Name Syntax..........................................6
5.3 Examples....................................................6
6. Security Considerations.........................................6
7. References......................................................7
7.1 Normative References........................................7
7.2 Informative References......................................7
8. Acknowledgments.................................................8
9. Author's Addresses..............................................9
10. Full Copyright Statement.......................................9
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1. Introduction
There is currently a need for a mechanism to identify the
originating party of a voice mail message, outside of the "FROM"
header information. The telephone number and name of the caller are
typically available from the telephone network, but there is no
obvious header field to store this in an Internet Mail message.
This information is intended for use when the VPIM message format is
used for storing "Call Answer" voice messages in an Internet Mail
message store, i.e. the calling party leaves a voice message for the
recipient, who was unable to answer the call.
[VPIMV2R2] suggests the originating number be included as an
Internet address, using the first method shown below. There are
several other ways to store this information, but they all involve
some manipulation of the "From" field. For example:
1. From: "416 555 1234" <non-mail-user@host>
2. From: "John Doe" <4165551234@host>
3. From: unknown:;
As a result, it is useful to be able to store the calling party's
name and number as presented to the called party without
manipulation. This would allow future generation of the proper
Internet address, and also display of this information to the
recipient. Note that there is no requirement to store meta-data
(e.g., type of number, presentation restricted) as this information
is not presented to the called party and is generally not available
to voice mail systems. The intent is to store the information
available to an analog (non-ISDN) phone (e.g., per [T1.401] in North
America).
[RFC2076] currently lists "phone" as an Internet message header
which would hold the originating party's telephone number, but it is
listed as "non-standard", i.e. usage of this header is not generally
recommended. It also has no defined format, making the information
unparsable. There is no similar entry for the originator's name.
It is proposed that two new message header fields be included to
hold this information, namely the Calling Line Identification
("Caller-ID"), and Caller Name ("Caller-Name").
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119.
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3. Calling Line Identification Field
The Calling Line Identification header ("Caller-ID") is to hold
sufficient information for the recipient to call back, or reply to,
the sender of the message. This leads to two distinct
possibilities: internal and external calling.
Note that for both possibilities, the number field MUST contain only
the digits of the number and MUST be representable using the
American Standard Code for Information Interchange [ASCII] character
set; it does not include any separating character (e.g. "-").
It is expected that default, and likely most common case, will not
have any numbering plan semantic associated with the number.
However, in the case that it is known, an optional "NumberingPlan"
parameter MAY be used to indicate the semantic.
3.1 Internal Call
For an internal call (e.g. between two extensions within the same
company), it is sufficient to relay only the extension of the
calling party, based on the company dialing plan.
3.2 External Call
For an international call, the calling partyØs number must be the
full international number as described in [E.164], i.e. Country Code
(CC), National Destination Code (NDC) and Subscriber Number (SN).
Other information, such as prefixes or symbols (e.g. "+"), MUST NOT
be included. This requires provisioning for up to 15 digits.
For a call within North America, it is also suggested to support 15
digits per [T1.625]. However, some service providers may only
support 10 digits as described in [T1.401] and [GR-31-CORE]. Though
it is desirable that an international number NOT be truncated to 10
digits if it contains more, it is recognized that this will happen
due to limitations of various systems.
Also note that the date and time can be included with the calling
partyØs telephone number per [T1.401]. This MAY be used, as there
is an existing "Date" Internet header to hold this information. It
is a local implementation decision whether this time or the local
system time be recorded in the "Date" header.
Note that the other defined fields available to non-analog systems
(e.g., subaddress, redirecting number), as well as the meta-data,
are not intended to be stored in this header.
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3.3 Numbering Plan
In this baseline case (i.e., analog lines), no numbering plan
information is known or implied. However, in the case that a
numbering plan is known, an optional "NumberingPlan" parameter MAY
be used to indicate the semantic. Only two semantics are defined Ï
"local" and "e164". "local" is the default if no numbering plan
semantic is included. Further, "local" has meaning only within the
FQDN of the sending system identified in the RFC 2822 "From" field.
"e164". "e164" indicates that the number is as described in
[E.164]. "x-" may be used to indicate vendor specific dialing plans.
4. Caller Name Field
The name of the person sending the message is also important. If
available, it is to be included whether the call is internal or
external. This field may not be available on an international call.
Further, the exact format for this field is typically a service
provider option per [T1.641]. It is possible for the callerØs name
to be sent in one of several character sets depending on the service
provider signaling transport (e.g., ISDN-UP, SCCP, TCAP). These
include:
1) International Reference Alphabet (IRA), formerly know as
International Alphabet No.5 or IA5 [T.50]
2) Latin Alphabet No. 1 [8859-1]
3) American National Standard Code for Information Interchange
[ASCII]
4) Character Sets for the International Teletex Service [T.61]
Of these, the IRA and T.61 character set contains a number of
options that help specify national and application oriented
versions. If there is no agreement between parties to use these
options, then the 7-bit character set in which the graphical
characters of IRA, T.61 and ASCII are coded exactly the same, will
be assumed. Further, the 7-bit graphical characters of [8859-1] are
the same as in [ASCII].
Note that for delivery to customer equipment in North America, the
calling name MUST be presented in ASCII per [T1.401].
As a result, for the caller name header defined in this document,
characters are represented with ASCII characters. However, if a
name is received that cannot be represented in 7-bit ASCII, it MAY
be stored using its native character set as defined in [RFC2047].
In the networks, the length of the name field MUST NOT exceed 50
characters, as defined in [T1.641]. However, service providers may
chose to limit this further to 15 characters for delivery to
customer equipment, e.g., [T1.401] and [GR-1188-CORE].
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5. Formal Syntax
Both Calling Line Identification and Caller Line follow the syntax
specification using the augmented Backus-Naur Form (BNF) as
described in [RFC2234]. While the semantics of these headers are
defined in sections 4 and 5, the syntax uses the ÕunstructuredØ
token defined in [RFC2822]:
unstructured = *([FWS] utext) [FWS]
5.1 Calling Line Identification Syntax
"Caller-ID" ":" 1*DIGIT [ "," "NumberingPlan="
( "local" / "e164" / ietf-token / x-token ) ] CRLF
ietf-token := <An extension token defined by a
standards-track RFC and registered
with IANA.>
x-token := <The two characters "X-" or "x-" followed, with
no intervening white space, by any token>
5.2 Caller Name Syntax
"Caller-Name" ":" unstructured CRLF
5.3 Examples
To: +19725551212@vm1.mycompany.com
Caller-ID: 6137684087
Caller-Name: Derrick Dunne
To: 6137637582@nortelnetworks.com
Caller-ID: 6139416900
Caller-Name: =?ISO-8859-1?Q?Jean_Chr=E9tien?=
6. Security Considerations
There are a few scenarios of how this mechanism may fail that must
be considered. The first is mentioned in section 3.2 - the
truncation of an international number to 10 digits. This could
result in a misinterpretation of the resulting number. For
instance, an international number (e.g. from Ireland) of the form
"353 91 73 3307" could be truncated to "53 91 73 3307" if received
in North America, and interpreted as "539 112 3456" - a seemingly
"North American" style number. Thus leaving the recipient with the
incorrect information to reply to the message Ï and possibly with an
annoyed callee at the North American number.
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The second scenario is the possibility of sending an internal
extension to an external recipient when a Call Answer message is
forwarded. This poses two problems, the recipient is given the
wrong phone number, and the company's dialing plan could be exposed.
The final concern deals with exercising character options that are
available in coding the Calling Name field. An international system
may send a message with coding options that are not available on the
receiving system. Thus giving the recipient an incorrect Caller
Name.
Note that unlisted and restricted numbers are not a concern as these
header fields are defined to contain what the called party would see
(e.g., 'Private Name'), as opposed to the complete details exchanged
between service providers.
However, it must also be noted that this mechanism allows the
explicit indication of phone numbers in the headers of an email
message (used to store voice messages). While the rationale for
this is reviewed in section 1, the recipient of this message may not
be aware that this information is contained in the headers unless
the userØs client presents the information. Its use is intended to
be informative as it is when it would appear on a telephone screen.
7. References
7.1 Normative References
[VPIMV2R2] Vaudreuil, Greg, Parsons, Glenn, "Voice Profile for
Internet Mail, version 2", <draft-ietf-vpim-vpimv2r2-05.txt>,
February 2002.
[RFC2047] K. Moore, "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text", RFC
2047, November 1996
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001.
[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and
Demon Internet Ltd., November 1997
7.2 Informative References
[RFC2076] Palme, "Common Internet Message Headers", RFC 2076,
February 1997
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[E.164] ITU-T Recommendation E.164 (1997), "The international public
telecommunication numbering plan"
[T.50] ITU-T Recommendation T.50 (1992), "International Reference
Alphabet (IRA)"
[T.61] CCITT Recommendation T.61 (1988) (Withdrawn), "Character
Repertoire and Coded Chaacter Sets for the International Teletex
Service"
[8859-1] ISO/IEC International Standard 8859-1 (1998), Information
Technology Ï 8-bit single-byte coded graphic character sets Ï Part
1: Latin Alphabet No. 1
[ASCII] American National Standards Institute (ANSI), Coded
Character Set - 7-Bit American National Standard Code for
Information Interchange, ANSI X3.4, 1986.
[T1.401] American National Standards Institute (ANSI),
Telecommunications Ï Network-to-Customer Installation Interfaces Ï
Analog Voicegrade Switched Access Lines with Calling Number
Delivery, Calling Name Delivery, or Visual Message-Waiting Indicator
Features, ANSI T1.6401.03-1998
[T1.625] American National Standards Institute (ANSI),
Telecommunications - Integrated Services Digital Network (ISDN) Ï
Calling Line identification Presentation and Restriction
Supplementary Services, ANSI T1.625-1993
[T1.641] American National Standards Institute (ANSI),
Telecommunications - Calling Name Identification Presentation, ANSI
T1.641-1995
[GR-1188-CORE] Telcordia Technologies, "CLASS Feature: Calling Name
Delivery Generic Requirements", GR-1188-CORE, Issue 2, December 2000
[GR-31-CORE] Telcordia Technologies, "CLASS Feature: Calling Number
Delivery", GR-31-CORE, Issue 1, June 2000
8. Acknowledgments
The previous authors of drafts of this document were Derrick Dunne
and Jason Collins. The current authors would like to thank Derrick
and Jason for their contributions.
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9. Author's Addresses
Glenn Parsons
Nortel Networks
P.O. Box 3511, Station C
Ottawa, ON K1Y 4H7
Phone: +1-613-763-7582
Email: gparsons@nortelnetworks.com
Janusz Maruszak
Phone: +1-416-651-4448
Email: jjmaruszak@sympatico.ca
10. Full Copyright Statement
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